KNOWITALL: Thursday’s Top 7 Stories at NBC News

1. EXCLUSIVE: Witness in S.C. shooting considered erasing video

The bystander who filmed a police officer shooting an apparently unarmed black man in the back in North Charleston thought about erasing the cellphone recording over fears of retaliation. The video recorded by Feidin Santana on Saturday shocked the nation when it was released this week. The footage resulted in Officer Michael Slager being arrested and charged Tuesday with the murder of Walter Scott. Read more in NEWS.

2. Will the convicted Boston bomber get the death penalty?

A jury found Dzhokhar Tsarnaev guilty Wednesday of all 30 counts against him in the 2013 Boston Marathon bombings. The jury that convicted Tsarnaev will now consider whether he should be put to death. The trial's penalty phase could begin next week. Read more in NEWS.

3. Storm brings tornadoes, hail and winds across Midwest, South

A monster storm peppered a 1,500-mile arc with 10 reported tornadoes, grapefruit-sized hail and winds of up to 80 mph Wednesday — and forecasters warned millions of Americans should brace for a second round Thursday. Stretching from Texas through North Carolina, the storm system has the potential to be the biggest severe weather event so far this spring, according to The Weather Channel. Read more in NEWS.

4. High levels of cancerous gas found in fracking area

Levels of radon — an invisible, odorless radioactive gas — have been rising measurably in Pennsylvania since the controversial practice of fracking started there, researchers reported Thursday. The study cannot directly link fracking with the raised radon levels — but residents still need to be aware take action to get it out of their homes, the researchers say. Read more in HEALTH.

5. French TV network TV5Monde hit by 'Islamist' hackers

A cyberattack by an "Islamist group" knocked a French TV network off the air on Wednesday night, the broadcaster's director said. TV5Monde said that 11 of its channels, websites and social media pages were hacked at around 10 p.m. local time (4 p.m. ET). The network's website featured a maintenance message as of early Wednesday morning. Read more in NEWS.

6. Obama to announce support for removing Cuba from terror list

President Obama is expected to announce that he is accepting a recommendation from the State Department to take Cuba off the State Sponsors of Terror list, sources told NBC News. The announcement, which could come as soon as Thursday, would coincide with Obama meeting Cuban President Raul Castro at a Latin American summit in Panama on Friday and Saturday. Read more in POLITICS.

7. White House backs banning ‘conversion therapy’ for minors

The White House has formally backed a call to end psychiatric treatments intended to "cure" gay minors, denouncing so-called conversion therapy for its "potentially devastating effects on the lives of transgender as well as gay, lesbian, bisexual, and queer youth." A petition for support was submitted to the White House in late December after a transgender Ohio teen committed suicide. Read more in NEWS.

We fully support efforts to ban the use of conversion therapy for minors-it's neither ethically/medically appropriate http://t.co/R7IV528kDW